Production of metal products directly from underground ore deposits

ABSTRACT

A process for producing metal compounds directly from underground mineral deposits including steps of forming a borehole at a site into a mineral deposit containing metal compounds, inserting a slurry-forming device having a nozzle into the borehole adapted to direct pressurized water through the nozzle into the mineral deposit, supplying pressured water through the nozzle into the mineral deposit forming a mineral slurry containing metal compounds, extracting the mineral slurry containing metal compounds through the borehole, leaching the mineral slurry converting the metal compounds to a soluble form in a leach solution, and removing metals and metal compounds by treating the leach solution with an extraction treatment removing the metal products. Steps of leaching the mineral slurry and removing metal products are performed at a location remote from the borehole site. In one alternative, the step of removing metal products from mineral slurry is accomplished by pyrometallurgical processes.

This application is a continuation of U.S. patent application Ser. No.12/695,045 filed Jan. 27, 2010, which claims the benefit of U.S. PatentApplication 61/147,502, filed on Jan. 27, 2009, which is incorporatedherein by reference.

BACKGROUND AND SUMMARY

Mineral deposits containing metal compounds from which metal productscan be made are presently found in various geographic locations and inore veins of quite varying depth. The mineral deposits in the past havebeen removed from such ore veins either by open pit mining or shaftmining. In locations where the mineral deposit is located close to thesurface of the earth, the overburden is removed by excavation to reachthe ore deposit and the ore removed by open pit mining. This type ofmining typically involves using very large and expensive draglines orother excavating equipment to remove the overburden and the ore deposit.Where the ore vein is deeper in the earth so that it is not practical toremove the overburden to reach the mineral deposits, shaft mines areemployed by digging tunnels and shafts so that miners and equipment canreach the ore deposit, and the ore deposit removed by the miners andequipment through the tunnels and/or shafts.

With either open pit or shaft mining, the mineral deposit must be ofsuch depth to make it economical to either remove the overburden or digthe tunnel and shafts to reach the ore deposit. Additionally, ore veinsunderground vary in depth along their run, and as a result, the miningonly continues to where the depth of the ore vein narrows to the pointwhere the overburden can no longer be economically removed or the oredeposit can no longer be reached underground with miners and availableequipment. These factors have greatly limited the ore deposits that canbe commercially removed from the ground.

Furthermore, open pit mining and shaft mining have been criticized forboth immediate and ongoing environmental concerns, including theirimpact on erosion, surface and underground water quality, and theaesthetic impact on mined and surrounding landscape and land values.Further, many mineral deposits exist beneath areas that areenvironmentally sensitive areas such as national or state parks,pristine lakes, recreational areas, urban areas, wetlands, and pristineand used surface areas where permits cannot presently be obtained toremove underground mineral deposits. These latter mineral deposits havebeen before now inaccessible because the prior methods available forremoving the mineral deposits impacted the local environment and/orpotentially damaged the natural or manmade resource above the mineraldeposit. Increasing awareness of environmental concerns and desire tomaintain various natural resources alone has caused fewer permits forremoval of desired mineral deposits to be granted.

Additionally, whether open pit or shaft mining is employed, ore removedfrom underground mineral deposits had to be processed to remove desiredmetal or metal compounds at the mine site. In the past, transportingores from the mine site was not possible for a commercially viablemining operation. Such processing of the ore from the mineral depositexacerbated the environmental impact by the need to process the removedore at the mine site. Processing of the ore at the mine site may involveseparation of the useful metals and metal compounds from undesirableminerals also present in the mineral deposit with environmentallysensitive chemicals. Such processing also likely involved storage ordisposal of various mine wastes at the mine site on an ongoing basis.

Accordingly, there remains a need for a method of producing metals andmetal compounds from mineral deposits that were not previouslycommercial accessible because of the costs of reaching the ore vein, orthat the nature of the land areas under which the ore vein lie made itenvironmental impermissible to remove the desired ore deposit.

Disclosed herein is a process for producing metal product directly frommineral deposits without open pit or shaft mining. This process isparticularly useful in removing manganese-bearing deposits and othersimilar mineral deposits where the ore in the mineral deposit can beformed directly into a slurry by injection of water under pressure intothe mineral deposit. In some cases, explosives or other means may beused in addition to the water pressure to break up the mineral depositand facilitate removal to the mineral deposit in a water slurry througha borehole. The method also includes transporting to a remote location,as well as processing the formed and extracted water slurry at theremote location to form a product of metal compounds that can be furtherprocessed in a furnace or other facility.

For removal and processing of metal-bearing ore deposits from anenvironmentally sensitive location, the present method may comprise thesteps of:

(a) forming a borehole from an accessible site into a mineral depositcontaining metal compounds;

(b) inserting a slurry-forming device having a nozzle into the boreholeadapted to direct pressurized water through the nozzle into the mineraldeposit;

(c) supplying pressured water through the nozzle of the slurry-formingdevice into the mineral deposit forming a mineral slurry containing themetal compounds from the mineral deposit;

(d) extracting the mineral slurry containing the metal compounds throughthe borehole;

(e) transporting the mineral slurry away from the borehole to a locationremote from the site;

(f) leaching the extracted mineral slurry at the remote location toconvert the metal compounds to a soluble form in a leach solution; and

(g) removing metal compounds by treating the leach solution with anextraction treatment adapted to remove the metal compounds.

Additionally, in the transporting step the mineral slurry may betransported in removed form or after partial water removal. Thistransporting step is particularly useful in removing mineral depositsfrom environmental sensitive areas and, in any event, may be used inallowing the leaching and removal steps to be performed at one locationon mineral slurries extracted through a number of boreholes in differentparts of the same or different ore veins. The mineral slurry may betransported by at least one device selected from a group consisting oftruck, rail, and pipeline to the remote location where the leaching andremoval steps are performed.

The present process for producing metal compounds may be used for miningmineral deposit containing oxides of at least one metal selected fromthe group consisting of manganese, cobalt, copper, iron, chromium, lead,nickel, magnesium, platinum, palladium, gold, silver, aluminum, lithium,molybdenum, tungsten, uranium, vanadium, zinc, and zirconium.

The pressure of the injected water may be any desirable or usefulpressure effective to form the mineral slurry of the manganese mineraldeposit in a particular ore vein. The water pressure, for example, maybe between 1000 and 2500 pounds per square inch (psi). The method isuseful with ore veins from narrow depths up to several hundred feet indepth. Similarly, the method is commercially feasible with ore veinsthat vary widely in depth, thus permitting removing of ore from mineraldeposits not previously possible and to an extent not previouslypossible.

The present method may be used for producing metal products directlyfrom underground mineral deposits that are capable of being broken up bythe slurry-forming device to create the mineral slurry. The method mayinvolve, where desired and permissible, detonating explosives or usingother auxiliary devices in the underground mineral deposit to assist inbreaking-up the ore deposit and forming the water slurry.

In one alternative, the method may be used also by forming more than oneborehole where the first borehole is generally vertical from the surfaceinto the mineral deposit and the second borehole is slanted so as tointersect the first bore in the ore deposit. The slurry-forming devicecan be inserted through the second slant borehole to increase the rangeto which water can be injected under pressure into the ore body, and theformed mineral slurry can be removed from the ore deposit through thefirst bore hole. This embodiment may increase the range of the removalof ore from certain ore veins through a borehole site. Alternatively,the first borehole may be partially predrilled in a slant borehole toallow the range of removal of mineral deposits from the ore vein from agiven borehole site.

The method may include, before leaching, and either before or afterperformance of the transporting step, a step of grinding particulatematter in the extracted mineral slurry to a particle size of about 80%smaller than 100 mesh, or about 80% smaller than 200 mesh.

The step of leaching the mineral slurry may include leaching the mineralslurry with acids to put desired metal compound into solution. Forexample, with extracted mineral slurry of the metal oxides of manganese,the acid may be sulfurous acid (H₂SO₃) formed by dissolving SO₂ inwater. Additionally, the leach solution may include at least onereducing agent selected from a group consisting of SO₂, carbon, reducingsugar, molasses, and a combination of two or more thereof. The leachsolution may have a pH of 3 or below.

After the step of leaching the mineral slurry placing desired metalcompounds in solution, the process may include the step of chemicallytreating the leach solution with oxidizing agents to produce manganeseoxide and/or other metal products. Alternatively or in addition, theprocess may include the step of chemically treating the leach solutionwith reducing agents producing metallic manganese.

After the step of leaching the extracted mineral slurry, the process mayinclude the step of treating the leach solution with one or moretreatments to remove selected metals or other metal compounds.Additionally, the step of removing metals and/or metal compounds ofmanganese may comprise electrochemically plating the manganese metalproduct out of solution or treating the leach solution to precipitatethe manganese metal product from solution.

Alternatively, the extracted mineral slurry may be processed bypyrometallurgical processes to remove the metal compounds from themineral slurry. In this alternative, the process for producing metalcompounds directly from underground mineral deposits in anenvironmentally sensitive location may include the steps of:

(a) forming a borehole from an accessible site into a mineral depositcontaining metal compounds;

(b) inserting a slurry-forming device having a nozzle into the boreholeadapted to direct pressurized water through the nozzle into the mineraldeposit;

(c) supplying pressured water through the nozzle of the slurry-formingdevice into the mineral deposit forming a mineral slurry containing themetal compounds from the mineral deposit;

(d) extracting the mineral slurry containing the metal compounds throughthe borehole;

(e) transporting the mineral slurry away from the borehole to a locationremote from the site;

(f) physically separating the extracted mineral slurry at the remotelocation; and

(g) removing metal compounds by treating the mineral slurry by apyrometallurgical extraction treatment adapted to remove the metalcompounds.

Prior to the step of physically separating the mineral slurry, theprocess may include grinding particulate in the mineral slurry to aparticle size of about 80% smaller than 100 mesh, and may includegrinding to a particle size of about 80% smaller than 200 mesh. Afterthe step of physically separating the mineral slurry, water may beremoved from the mineral slurry and the resulting ore material thenmixed with at least one reducing agent selected from a group consistingof coal, coke, coke-breeze, char, reducing sugar, molasses, and acombination of two or more thereof. Alternatively or in addition, watermay be removed from the mineral slurry and the ore material may be mixedwith at least one additive selected from a group consisting of calciumoxide, limestone, soda ash, Na₂CO₃, NaHCO₃, NaOH, borax, NaF, fluorspar,CaF₂, aluminum smelting industry slag and a combination of two or morethereof.

The step of removing metal compounds may be performed in a rotary hearthfurnace. Alternatively, the step of removing metal compounds may beperformed in an electric arc furnace, a blast furnace, or an inductionfurnace.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing steps of a method for producing metalfrom a mineral deposit; and

FIG. 2 is a diagrammatical partial section view of a borehole miningoperation.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to FIG. 1, a method is disclosed for producing metals andmetal compounds that may be used to extract metal products fromenvironmentally sensitive areas. As shown in FIG. 1, the method mayinclude steps of:

-   -   (a) forming a borehole at an accessible site into a mineral        deposit, the mineral deposit containing metal oxides such as        metal oxides of manganese;    -   (b) inserting a slurry-forming device having a nozzle into the        borehole, the device adapted to directing pressurized water        through the nozzle into the mineral deposit;    -   (c) supplying pressured water through the nozzle into the        mineral deposit;    -   (d) forming a mineral slurry containing metal oxides, such as        metal oxides of manganese;    -   (e) extracting the mineral slurry through the borehole to the        surface;    -   (f) optionally, separating water from the extracted mineral        slurry, which may be recycled to a water storage tank;    -   (g) optionally, forming a filter-cake of the mineral slurry        having a water content of between about 8% and 10%;    -   (h) transporting or conveying the mineral slurry to a processing        location;    -   (i) leaching the mineral slurry to convert the metal oxides to a        soluble form in a leach solution; and    -   (j) removing metal compounds of manganese by treating the leach        solution with an extraction treatment adapted to remove metal        products, or other hydrometallurgical leaching techniques to        extract metal products.

Alternatively, instead of removing metal compounds from a leachsolution, desired metal compound may be removed from the mineral slurryusing pyrometallurgical processes. After transporting, as shown in thealternative process in FIG. 1, the process may include steps ofupgrading the mineral slurry by physical separation. After de-wateringthe mineral slurry, the resultant ore material may be processed usingpyrometallurgical extraction as discussed below.

The present method involves first forming a bore hole into a mineraldeposit with suitable drilling equipment at a select borehole site thatis environmentally permitted, and lowering into the mineral depositthrough the borehole a slurry-forming device having a nozzle throughwhich pressurized water can be injected into the mineral deposit. Forremoval of manganese-bearing ore from such a mineral deposit, the waterpressure may be between 1000 and 2500 psi. In any event the pressurizedwater should be sufficient to break up the ore in the mineral depositand form a mineral slurry that can be pumped through the borehole to thesurface at the borehole site. The range of extraction of ore from themineral deposit will depend on the softness of the mineral deposit andthe extent and direction of the water pressure. The slurry-formingdevice may permit the nozzle to be controlled and directed in anydesired direction, and the nozzle may be rotated about the axis of theborehole to carve out an approximately circular work area in the orevein around the borehole, and may be moved along the borehole to extendthe work area and volume of ore removed from the borehole site.

The present method is effective where the mineral deposit is in friableform, granular form, or other form capable of being broken up by thepressurized water from the slurry-forming device to create the mineralslurry. Higher pressure water may be used for harder or denser mineraldeposits, or where a larger work area of extraction may be desired froma borehole. In some cases, explosives or other supplemental means may beused where desired and permissible to assist the water pressure informing the mineral slurry in the mineral deposit.

In one embodiment, the method could be performed with the mineraldeposit of metal compounds of manganese formed in an mineral depositabout 200 feet to 400 feet beneath the surface of an overburden in theEmily District of Minnesota, where the mineral deposit containsmanganese ore including pyrolusite (MnO₂) and magnanite (MnO(OH)). Suchmanganese deposits may contain “sand-like” particles in a granular formcapable of being broken up by water at a pressure between about 1000 and2500 psi. In alternative locations, the mineral deposit may containoxides of manganese, cobalt, copper, iron, chromium, lead, nickel,magnesium, platinum, palladium, gold, silver, aluminum, lithium,molybdenum, tungsten, uranium, vanadium, zinc, and zirconium.

As shown in FIG. 2, a borehole drilling device 10 may include ahydraulic slurry-forming device 20 having a nozzle 22 inserted into adesired work area 24 in a mineral deposit through casing pipe 30. Theborehole drilling device 10 may have a drill bit 40 at its lower endadapted to bore a borehole cavity 42 that is somewhat larger in diameterthan the hydraulic slurry-forming device 20 and the casing pipe 30. Asshown in FIG. 2, the drilling device 10 may drill through the cap rock44, through the desired work area 24 in the mineral deposit, and intothe bedrock 46 forming a sump 48. An eductor section 50 is positioned inthe casing pipe 30 below the hydraulic slurry-forming device 20. Aninner pipe 60 extends through the casing pipe 30 in connection with theeductor section 50 and forming annular conduit 70 between the inner pipe60 and the casing 30, which is in connection with the nozzle 22 of theslurry-forming device. The casing pipe 30 and inner pipe 60 extend froman work area in a mineral deposit, to the surface, and may be formed byconnecting a plurality of pipe sections end to end. The inner pipe 60forms an outlet slurry passage for removing the mineral slurry from themineral deposit, and the conduit 70 forms an inlet water passage fordelivering water 72 to the nozzle 22 of the slurry-forming device 20 inthe mineral deposit.

A pump 80 is provided in connection with the annular conduit 70 fordelivering pressurized water into the conduit 70 to the hydraulicslurry-forming device 20. In operation, the pump may provide betweenabout 400 and 1000 gallons per minute (gpm) water flow. In onealternative, the pump provides 750 gpm of water at 2500 psi to thenozzle 22 of the slurry-forming device. The pressurized water flow,which may be fitted with a suitable regulator, is directed through thenozzle 22 into the work area in the mineral deposit transverse to theborehole. As the water passes through the nozzle 22, the flowaccelerates to a flow sufficiently powerful to break and scale away theore from the mineral deposit in the work area 24 to form a mineralslurry 82. The water pressure through the nozzle 22 may be regulatedbetween about 1500 and 2500 psi. Alternatively, the water pressurethrough the nozzle 22 may be regulated between about 800 and 1500 psi.The loosened material from the mineral deposit is fluidized throughmixing with the injected water to form the mineral slurry 82 in the workarea.

The upper end of the drilling device 10 may include a swivel joint 100and turntable 102 capable of rotating at least a portion of the drillingdevice. The drilling device may be supported by a suspension 104 such asa crane, derrick, or other suspension. In operation, the drilling devicemay be rotated to turn the drill bit 40 for extending the borehole intothe mineral deposit. Alternatively or in addition, the hydraulicslurry-forming device 20 may be rotated for rotating the nozzle 22 in anapproximately circular cutting path around the borehole. By rotating thenozzle around the axis of the borehole, and by raising and lowering thenozzle in the borehole, an approximately cylindrical shaped work areacavity 110 may be formed around the borehole in the mineral deposit 24by the pressurized water flow 72 fluidizing material from the depositand forming the mineral slurry 82 for extraction.

Water pumped through the inlet water conduit 70 toward the work areathat does not exit the nozzle is directed to the eductor 50 having adischarge into the inner pipe 60. The flow of water through the eductor50 provides suction to draw mineral slurry from the work area into theinner pipe 60. The mineral slurry and water are sucked through an inletinto the inner pipe 60 and transported up to the surface at the boreholesite through the inner pipe 60. The mineral slurry may be directed to aclarifier tank 90 or other suitable container at the borehole site wherewater may be removed and the slurry concentrated. As the mineralparticulate settles to the bottom of the tank 90, water may be filteredfrom the tank and pumped back to the work area in the mineral depositthrough the conduit 70. By re-using the water, make-up water may bereduced to a minimum and the method becomes even more environmentalcapable as essentially a closed loop system for removing the mineralslurry from the mineral deposit. In one example, additional water use inoperation of the formation and removal of the mineral slurry was limitedto 1000 gallons per day. Water may be supplied in a water storage tank,not shown, such as a 20,000 or 40,000 gallon storage tank.

In one embodiment, the flow rate of mineral slurry through the innerpipe 60 may be between about 400 and 800 gpm, which may be directed tothe clarifier tank 90. The extracted mineral slurry may be between about10% and 20% solids, and may be greater than 20%. For certain mineraldeposits, the extracted mineral slurry may be less than 10% solids.

For larger mineral deposits or directional ore veins, a directionalborehole may be formed slanted and/or extended generally horizontallythrough the ore vein. In certain directional boreholes, theslurry-forming device may be moved along the borehole without beingrotated. Also, a plurality of deviated boreholes may be drilled from one“mother” bore, each deviated borehole extending the inclination and/orhorizontal reach into the mineral deposit as desired to increase thevolume of removed mineral ore.

The overall structure and operation of a borehole drilling apparatus andslurry-forming device may be as described in U.S. Pat. Nos. 4,059,166,6,460,936, and 6,688,702, the disclosures of which are incorporatedherein by reference for appropriate constructional and operationaldetails for purpose of best mode of carrying out the method of thepresent disclosure.

The method may be used also by forming a first borehole substantiallyvertically from the surface into the mineral deposit and a secondborehole slanted so as to intersect the first bore in the mineraldeposit, not shown. The slurry-forming device may be inserted throughthe second slant borehole to increase the range to which water can beinjected under pressure into the mineral deposit, and the formed mineralslurry can be removed from the mineral deposit through the first borehole. For certain mineral deposits, this embodiment may increase therange of the removal of metal compounds from the ore deposit.

In another alternative, a plurality of boreholes may be provided forwater injection and at least one borehole provided for mineral slurryextraction. In one embodiment, not shown, four boreholes are providedfor water injection, arranged approximately in quadrants of a work area.An extraction borehole is provided in approximately centrally located inthe work area, as desired, for extraction of slurry. The extractionborehole may not be as deep as, or may be deeper than the boreholesthrough which water is injected into the mineral deposit.

In any case, after the mineral slurry is extracted from the mineraldeposit through one of the boreholes or the inner pipe 60 of a givenborehole, the mineral slurry is processed to remove the desired metalproducts. In clarifier tank 90, for example, water from the mineralslurry may be filtered, removed and recycled. The mineral slurry maypass through a screen such as a screen having 1/16 inch openings toscreen out larger ore pieces. Then additional water may be removed usinga cyclone, settling tank, and/or a thickener tank which increases thesolids in the slurry from about 10% solids to between about 45% and 75%solids. The mineral slurry may be further dewatered in a filter press toform a filter cake of mineral slurry having a moisture content betweenabout 8% and 10%. Alternatively, the moisture content of the filteredmineral slurry may be less than 8% or more than 10% as desired in theparticular embodiment. The water removed from the mineral slurry may bepumped into the water storage tank, or may be pumped back to the workarea of the mineral deposit through annular conduit 70.

During the mining process, slightly more water may be extracted with themineral slurry from the mineral deposit than is injected through thenozzle. A net withdrawal of water from the work area produces a “cone ofdepression” in the work area. The depression may enable an inflow ormigration of pre-existing underground water towards the borehole areathat enables mineral slurry to flow toward the work area. The cone ofdepression may slow the outflow of mineral slurry away from the workarea.

For extracting minerals from environmentally sensitive and other areas,the extracted mineral slurry is transported away from the mine site tobe processed at a remote location as discussed below. The mineralslurry, either as extracted from the mineral deposit or afterconcentration, may be transported by truck, rail, pipeline, or acombination thereof to the remote location to remove the desiredcompounds.

To remove the desired compounds, the mineral slurry may be processed toform a leaching solution from which the desired metal compounds andother metal products may be removed. Alternatively, the desiredcompounds may be removed from the mineral slurry by a pyrometallurgicalprocess. The process of removing desired compounds from the mineralslurry may be performed at the borehole site as desired and permitted,or may be performed at the remote location.

Optionally, prior to leaching, or pyrometallurgical processing discussedbelow, the process may include grinding or otherwise reducing theparticle size of the ore in the mineral slurry to a particle size ofabout 80% less than 100 Tyler mesh, or a particle size of 80% less than200 Tyler mesh.

In one embodiment, the manganese mineral forms include pyrolusite (MnO₂)and magnanite (MnO(OH)) having the consistency of “sand-like” particleshaving a particle size in the range of about 10 mesh to about 500 mesh.In this deposit, the particles are porous, fine particles that may notrequire further grinding, and may need little preparation before thestep of leaching of the ore to form a leaching solution from whichmanganese metal may be extracted.

The mineral slurry may be leached to convert the metal oxides to asoluble form in a leach solution. The leach solution may be formed in asuitable leaching tank such as a tank having stifling blades, or otherstirred tank. The stirred tank may be adapted to a continuous leachingprocess, or may be adapted to a batch process.

The leach solution may be formed with approximately 10% manganese in anacidic solution. For leaching some mineral ores, the leach solution mayinclude between about 10% and 80% manganese. Alternatively, the leachsolution may include between about 5% and 10% manganese.

Leaching may be conducted using SO₂ gas, which acts with water to formsulfurous acid (H₂SO₃) to render the metal compounds in the mineralssoluble in solution. SO₂ gas may be introduced into the stirred mineralslurry through diffusers or spargers placed below the tank stirringblades. The SO₂ gas is passed through the manganese leach solution to apH of about 1. The leach solution may have between about 5% and 8% SO₂at a pH of about 1. The SO₂ addition is controlled to maintain the pH ofabout 1 for a processing period of about 10 minutes, after which timeabout 95% or more of the manganese is in solution. Alternatively,sulfuric acid (H₂SO₄) may be used to form the acidic leach solution withsimilar pH and percent manganese in solution. In any case, the manganeseleaching process is conducted at ambient temperature and atmosphericpressure in the leaching tank.

A reducing agent may be provided in the leach solution. The reducingagent may be SO₂, carbon, reducing sugar, molasses, or other reducingagents. The reducing agents reduce the oxidation state of the metaloxides in solution, such as from Mn(4+) to Mn(2+).

The manganese (Mn(2+)) in the acidic leach solution may be MnSO₄. Theleach solution may be chemically treated with oxidizing agents toproduce metal compounds, such as metal oxides. The manganese leachsolution may be treated with an oxidizing agent, such as H₂O₂, NaOCl,KMnO₄, or Na₂S₂O₈ or other oxidizing agent to form chemical manganesedioxide (MnO₂), or CMD in solution. Alternatively, the MnSO₄ may beelectrochemically oxidized to form electrolytic manganese dioxide, orEMD in solution. In yet another alternative, the MnSO₄, may be dried andcrystallized to form chemical grade MnSO₄ or fertilizer grade MnSO₄.

In yet another alternative, the process may include the step ofchemically treating the leach solution with reducing agents producingmetallic manganese. Then, electrochemically treating the leach solutionto plate out metallic manganese. The extraction treatment may be anelectrochemical treatment, such as electroplating the desired metal ontoa cathode.

After the desired metal compounds or other metal products are extractedfrom the leach solution, the leach solution may be reconditioned to thedesired pH and reused to process subsequent batches of mineral slurry.Mineral solids and solutions left over from the leaching process may beneutralized, if necessary with lime or limestone, for use ordisposition. Alternatively, the leach solution may be further used forsecondary processes. For example, the use of SO₂ gas dissolved in waterproduces a sulfate, which can be used to make ammonium sulfatefertilizer. After the desired metal products are removed from the leachsolution, ammonia may be added to form the ammonium sulfate.

As discussed above, the present methods may be used to make metalproducts directly from underground mineral deposits other than manganesewhere the ore vein can be broken up to form a mineral slurry. Thismethod may be suitable for use in making oxides of cobalt, copper, iron,chromium, lead, nickel, magnesium, platinum, palladium, gold, silver,aluminum, lithium, molybdenum, tungsten, uranium, vanadium, zinc, andzirconium directly from underground mineral deposits.

For ore from some mineral deposits, the leach solution may have a pH ofabout 3 or lower, and in certain alternatives may have a pH of about 5or lower. Additionally, certain ores from mineral deposits may be in theleach solution at temperatures and pressures higher than ambient torender the minerals soluble.

Some ores form mineral deposits containing a plurality of metals, eachhaving certain extraction techniques the present method may be used tomake two or more metal products of different metals from the mineralslurry. The mineral slurry may require multiple treatments each adaptedto removing specific metal products from the mineral slurry dependingupon the composition of the extracted ore. In some cases, certain leachsolution treatments may be used to remove undesired or other metals andmetal compounds that would contaminate the desired metal compound orother desired metal products. In other cases certain leach solutiontreatments may recover metal products for sale or use depending in parton market prices. For example, certain manganese ore deposits containvarious amounts of other metals and compounds such as iron, silica, andalumina which may be recovered if present in sufficient quantities tomake recovery commercially viable.

For example, iron may be removed from the leach solution by raising thepH of the solution to about 5 or greater by the addition of lime orother base, then adding an oxidizing agent, such as manganese oxide orother oxidizer to form an iron precipitate. The iron precipitate maythen be filtered from the solution as a metal product.

In another example, where a leach solution is formed containing nickeland manganese, it may be desired that nickel remain in solution andmanganese be removed. The manganese may be precipitated from the leachsolution by an addition such as ammonia and carbon dioxide, which formsMnCO₂. The manganese precipitate may be filtered from the solution toform the metal product.

Amounts of heavy metals such as nickel, arsenic, lead, cobalt, and otherheavy metals found in the ores may be removed from a leaching solutionform from the mineral slurry by adding sulfide to the leach solution toform precipitates that may be filtered from the solution to form themetal product.

Other impurities and undesired metals and compounds may be found in themineral ore which may be from a leaching solution form from the mineralslurry. Various chemical treatments may be applied as desired to removethe metal products from the leach solution. It is contemplated that theleach solution may be heated to a desired temperature and pressureaccording to the chemical treatment applied to form the desired metalproducts.

In some embodiments, after impurities and undesired compounds and metalsare precipitated from the solution, the leach solution may be treatedwith chemical or electrochemical techniques to plate out the desiredmetal compounds or other metal products from solution. Also, to producea metallic state, reducing agents may be provided in the leach solution.The reducing agents may be SO₂, carbon, reducing sugar, molasses, orother reducing agents. Alternatively, the leach solution may bechemically treated with oxidizing agents to produce metal products, suchas metal oxides.

In an alternative process, the mineral slurry may be processed usingpyrometallurgical extraction methods to remove the certain metalcompounds from the mineral slurry. The process may include grinding orotherwise reducing the particle size of the ore in the mineral slurry toa particle size of about 80% less than 100 Tyler mesh, or to a particlesize of 80% less than 200 Tyler mesh. To increase the concentration ofdesired metal compounds in the mineral slurry, the mineral slurry may beupgraded using physical separation processes to separate tailings suchas rock and other separable products from the slurry. The mineral slurrymay be upgraded using physical separation such as high intensitymagnetic separation, gravity separation, floatation, or other separatorsas desired. In some applications for processing at a location remotefrom the borehole site, the mineral slurry may be de-watered fortransportation. For grinding and physical separation processes themineral slurry may be reslurrified as desired.

After the step of physically separating the mineral slurry, the upgradedmineral slurry is de-watered, and the resulting ore material may bemixed with one or more reductants. The reducing agents may be selectedfrom a group consisting of coal, coke, coke-breeze, char, reducingsugar, molasses, and a combination of two or more thereof. Alternativelyor in addition, the mineral slurry is de-watered, and the resulting orematerial mixed with at least one additive selected from a groupconsisting of calcium oxide, limestone, soda ash, Na₂CO₃, NaHCO₃, NaOH,borax, NaF, fluorspar, CaF₂, aluminum smelting industry slag and acombination of two or more thereof. The ore material mixture may then befed into a furnace for extracting the desired metal compound. Thefurnace may be an electric arc furnace, blast furnace, inductionfurnace, or rotary hearth furnace at a temperature selected for thedesired metal compound.

In one application, a mineral slurry containing manganese ore may beprocessed in a rotary hearth furnace between approximately 1100 and1300° C. The de-watered manganese ore material may be mixed with areductant such as coal and a fluxing agent such as limestone.Optionally, the manganese ore material may be formed into briquettes.The manganese slurry may be processed in the furnace to produceferromanganese and/or silicomanganese, with other compounds and tailingsseparating as slag.

As discussed above, the mineral slurry may be processed at the boreholesite or transported away from the borehole site to be processed at aremote location. The mineral slurry may be transported by truck, rail,pipeline, or a combination thereof as extracted from the mineral depositor after removing part of the water from the slurry. By transporting themineral slurry to a location remote from the borehole site, the usechemicals, such as sulfurous acid and sulfuric acid in the leaching stepmay be managed in a location more environmentally suited to chemicalprocessing. Further, by including the transportation step in the method,one leaching and metal product recovery facility can service multipleborehole sites and a large volume of mineral slurry, vastly increasingthe productivity of the method in making metal products directly fromunderground mineral deposits.

In one embodiment, the mineral slurry is transported to the processinglocation in water tight dump trucks such as a 20 ton covered side dumptrucks. Prior to transporting, the concentrated mineral slurry may beformed into filter cakes, the filter cakes being loaded directly intotrucks or onto railcars. Alternately, the filter cakes may be loadedinto ore bags such as 2000 lb water tight sacks, which may betransported by truck or rail. In one alternative, the mineral slurry isnot formed into a filter cake and is transported by pipeline, themineral slurry having a solids content about 50% or greater.

The presently disclosed process may be used to recover metal productsdirectly from mineral deposits under environmentally sensitivegeographic areas. The process may include the steps of forming aborehole into a mineral deposit of ore containing metal compounds,inserting a slurry-forming device having a nozzle into the boreholeadapted to direct pressurized water through the nozzle into the mineraldeposit, supplying pressured water through the nozzle into the mineraldeposit forming a mineral slurry from an ore vein, and extracting themineral slurry through the borehole. Then, transporting the mineral orecontaining metal oxides away from the borehole to a location remote fromthe borehole site, leaching the metal oxides at the remote location toconvert the metal oxides to a water soluble form in a leach solution,and removing metal compounds and other metal products by treating theleach solution with an extraction treatment adapted to remove the metalsand/or metal compounds.

By transporting the mineral ore away from the mine site, chemicals usedat the borehole site and needed facilities may be substantially reduced.The slurry formation step may use water without chemical or otheradditions. The water may be taken from groundwater or surface sources.Additionally, it is contemplated that the water may be returned to theenvironment with little cleaning or water treatment required. By usingthe disclosed process and transporting the mineral slurry away from themine site, valuable mineral deposits may be extracted in environmentallysensitive areas with insignificant impact on the overlying surface area.

While the invention has been illustrated and described in detail withreference to the figures and foregoing description, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that one skilled in the art will recognize, and that it isthe applicants' desire to protect, all aspects, changes andmodifications that come within the spirit of the invention.

1. A process for producing metal compounds directly from undergroundmineral deposits in an environmentally sensitive area comprising thesteps of: (a) forming a borehole from an accessible site into anunderground mineral deposit containing metal compounds including oxidesof manganese beneath the environmentally sensitive area; (b) inserting aslurry-forming device having a nozzle into the borehole adapted todirect pressurized water through the nozzle into the mineral depositunder the environmentally sensitive area; (c) supplying pressured waterthrough the nozzle of the slurry-forming device into the mineral depositforming a mineral slurry containing the metal compounds from the mineraldeposit under the environmentally sensitive area; (d) extracting anddewatering the mineral slurry containing the metal compounds through theborehole in the environmentally sensitive area; (e) transporting thedewatered mineral slurry as extracted from the mineral deposit away fromthe borehole to a location remote from the environmentally sensitivearea; (f) leaching the extracted mineral slurry at the remote locationto convert the metal compound to a soluble form in a leach solution; and(g) removing metal compounds by treating the leach solution with anextraction treatment adapted to remove the metal compounds.
 2. Theprocess for producing metal compounds directly from underground mineraldeposits according to claim 1, where the mineral slurry is transportedby a device selected from a group consisting of truck, rail, pipeline,and a combination of two or more thereof.
 3. The process for producingmetal compounds directly from underground mineral deposits according toclaim 1 further comprising the step of: prior to the step of leachingthe mineral slurry, grinding particulate in the mineral slurry to aparticle size of about 80% smaller than 100 mesh.
 4. The process forproducing metal compounds directly from underground mineral depositsaccording to claim 1 further comprising the step of: prior to the stepof leaching the mineral slurry, grinding particulate in the mineralslurry to a particle size of about 80% smaller than 200 mesh.
 5. Theprocess for producing metal compounds directly from underground mineraldeposits according to claim 1, further comprising the step of: after thestep of leaching the mineral slurry, treating the leach solution withone or more treatments to remove selected metals and metal compounds. 6.The process for producing metal compounds directly from undergroundmineral deposits according to claim 1 where the step of leaching themineral slurry comprises leaching the mineral slurry to put desiredmetal compounds into solution.
 7. The process for producing metalcompounds directly from underground mineral deposits according to claim1 where the step of leaching the mineral slurry comprises leaching themineral slurry with sulfurous acid.
 8. The process for producing metalcompounds directly from underground mineral deposits according to claim1 where the leach solution comprises at least one reducing agentselected from a group consisting of SO₂, carbon, reducing sugar,molasses, and a combination of two or more thereof.
 9. The process forproducing metal compounds directly from underground mineral depositsaccording to claim 1 where the leach solution has a pH of 3 or lower.10. The process for producing metal compounds directly from undergroundmineral deposits according to claim 1 further comprising the step of:prior to the step of removing metal compounds, chemically treating theleach solution with oxidizing agents producing metal compounds.
 11. Theprocess for producing metal compounds directly from underground mineraldeposits according to claim 1 further comprising the step of: prior tothe step of removing metal compounds, chemically treating the leachsolution with reducing agents producing selected metal products.
 12. Theprocess for producing metal compounds directly from underground mineraldeposits according to claim 1 where the step of removing metal compoundscomprises electrochemically treating the leach solution removingselected metals or metal compounds.
 13. The process for producing metalcompounds directly from underground mineral deposits according to claim1 further comprising forming a second slanted borehole in theenvironmentally sensitive area intersecting the first borehole in themineral deposit containing metal compounds including oxides ofmanganese; where the step of inserting a slurry-forming device is intothe second borehole, and where the step of extracting is through thefirst borehole.
 14. A process for producing metal compounds directlyfrom underground mineral deposits in an environmentally sensitive areacomprising the steps of: (a) forming a borehole from an accessible siteinto an underground mineral deposit containing metal compounds includingoxides of manganese beneath the environmentally sensitive area; (b)inserting a slurry-forming device having a nozzle into the boreholeadapted to direct pressurized water through the nozzle into the mineraldeposit under the environmentally sensitive area; (c) supplyingpressured water through the nozzle of the slurry-forming device into themineral deposit forming a mineral slurry containing the metal compoundsfrom the mineral deposit under the environmentally sensitive area; (d)extracting and dewatering the mineral slurry containing the metalcompounds through the borehole in the environmentally sensitive area;(e) transporting the dewatered mineral slurry as extracted from themineral deposit away from the borehole to a location remote from theenvironmentally sensitive area; (f) physically separating the extractedmineral slurry at the remote location; and (g) removing metal compoundsby treating the mineral slurry by a pyrometallurgical extractiontreatment adapted to remove the metal compounds.
 15. The process forproducing metal compounds directly from underground mineral depositsaccording to claim 14, where the mineral slurry is transported by adevice selected from a group consisting of truck, rail, pipeline, and acombination of two or more thereof.
 16. The process for producing metalcompounds directly from underground mineral deposits according to claim14 further comprising the step of: prior to the step of physicallyseparating the mineral slurry, grinding particulate in the mineralslurry to a particle size of about 80% smaller than 100 mesh.
 17. Theprocess for producing metal compounds directly from underground mineraldeposits according to claim 14, further comprising the step of: afterthe step of physically separating the mineral slurry, mixing the mineralslurry with at least one reducing agent selected from a group consistingof coal, coke, coke-breeze, char, reducing sugar, molasses, and acombination of two or more thereof.
 18. The process for producing metalcompounds directly from underground mineral deposits according to claim14, further comprising the step of: after the step of physicallyseparating the mineral slurry, mixing the mineral slurry with at leastone additive selected from a group consisting of calcium oxide,limestone, soda ash, Na₂CO₃, NaHCO₃, NaOH, borax, NaF, fluorspar, CaF₂,aluminum smelting industry slag and a combination of two or morethereof.
 19. The process for producing metal compounds directly fromunderground mineral deposits according to claim 14, where the step ofremoving metal compounds is performed in a rotary hearth furnace in areducing atmosphere.